Process of producing sodium cyanid.



H. FREEMAN.

PROCESS OF PRODUCING SVODIUM CYANID. APPLICATION FILED APR23. l9l 8.

1 277,900. PatentedSept. 3, 1918.

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abhor/nu fll reeflwcn, by

i To all whom it may concern} I s ra'rns Parana orricn.

HORACE FREEMAN, E NIAGARA FALLS, ONTARIO, CANADA, ASSIGNOR '10 AMERICAN GYANAMID COMPANY, OFN'EW. YORK, Y., A CORPORATION OF MAINE.

rnocnss or rnonncr'ns SODIUM CYANID.

Be it known that I, HORACE Fnnnmnn, a subject of the King of Great Br tain, reslding at Niagara Falls, in the Provmcepf Ontario, and Dominion of Canada, have lnvented certain new and useful Improvements in- Processes of Producing Sodium Cyanid; and

I do hereby declare the following to be a full, clear, and exact description of the mvent1on, such as will enable others skilled in the art to which it appertains to make and use the same.-

This invention relates to a process of producing sodium cyanid from lime nitrogen and has for its object to improve the methods heretofore proposed.

' To these ends the invention consists in the 'novel steps'and combinations of steps con:

stituting the process, all as will be more fully hereinafter d sclosed and particularly pointed out inthe claims.

views- Figure 1 1s a diagrammatic sectlonal view of a furnace suitable for carrying out this invention and-- F1g.-2 1s an enlarged sectlonal detall vlew of a portion of the partsshown in Fig. 1.

1 indicates any suitable furnace preferably of the type shown,- and having a base portion 2 of refractory conducting material such as carbon, 3 a lining of refractory material, and 4t anouter wall of heat insulating material. The whole issupported on any suitable foundation 5, and a suitable conductor 6 leads current to the conducting bottom. 7 is a carbon electrode dependent in a restricted crucible 9. The sizeof the electrode and the dimensions of the crucible are so proportioned that a slight relative motionof the fused contents of the hearth with respect to the electrodes, causesa large variation in the current flowing through the furnace. The furnace is provlided with a suitable tap hole 11, connected with the crucible by a passage 10 and 12 represents a b ushing of iron lining said ta'p hole, 18 a hollow. block fitting said bushing; and 14 represents a Specification of Letters Patent.

Patented Sept. s, 1918; Application filed April 23, 1918. Serial No. 230,363. 7

tapered iron plug carried by the rod 15, ex-

melts and collectsas a molten pool 21 at the bottom of the crucible.

The charge of this furnace may consist of lime nitrogen, salt and calcium carbid in any suitable proportions, the mixture being'dependent upon the grade of the final product to be made, and amount of, attention to be given to the furnace operation. An example of a suitable charge is the following :Equal parts of lime nitrogen and salt to which is added approximately one twentieth 0f the weight of the mixture in ordinary calcium carbid. This said furnace charge may be" varied by changing the proportions of all three ingredients, but theabove'mix'ture represents an example of a practicable and economic furnace mixture.- By increasing the amount of salt in proportion to the lime nitrogen used above that mentioned, one obtains a furnace mixture which can be smelt: ed with less attention to exact operating conditions than heretofore, and it is more economical under certain circumstances to operate wlth a greater proportion of salt.

The calcium carbid may be replaced bya free carbon, preferably of such form as lamp black or slmllar carbonaceous material,

which has not been previously heated to a temperature higher than 800 C. The amount of such free carbon addition may be varledv'vi'thin rather wide limits but a satisfactory amount isusually about one twen-. tieth of the weight of lime nitrogen and salt in the charge.

I have discovered that when lime nitrogen as produced by the ordinary process and containing calcium. cyanamid, carbon, free lime, negligible amounts of other minor lmpurltles of no consequence, is-fused with common salt areaction takes-places in stages. 'In the first stage, the calcium cyanamid and the sodipm chlorid seem to suffer double. decompos1tion whereby sodium cyanamid and calcium chlorid is produced; This sodium cyanamid is'; not particularly stable and readily breaks down into other products yielding'gases and vapors of various kinds. If, however, chemically. active carbon is present, this said sodium cyanamid will combine with the active carbon to form sodium cyanid in accordance with the following equation- NaoN +o=eNaoN Now, I have found that at the temperature at which the sodium cyanamid was produced, the carbon in the lime nitrogen is still rather inert and only slowly'reacts with the sodium cyanamid. Rapid action of this more or less inert form of carbon seems to occur only at temperatures several hundred degrees above the formation temperature of the sodium cyanamid. There is, therefore, the possibility of having sodium cyanamid set free in the mass and'in contact with only the slow reacting form of carbon, thereby permitting decomposition of the sodium cyanamid with a consequent foaming and violent boiling of the furnace charge.

But, by causing the reaction or fusion to take place quite rapidly the time interval between the formation of sodium cyanamid at its temperature of formation and the formation of cyanid by reaction with carbon at the more favorable higher temperature may be made very short, thereby occasioning less decomposition and less foaming. In otherwords, a'rapid smelting furnace, or one usinga high energy density will oper' ate more efficiently and withless trouble than 'a slower melting furnace or one using a lower'density on the same charge. Since the quantity of sodium cyanamid in a free state atany one time may be made comparatively smaller by using the principle of rapid smelting, I'have found that .,..practically 'all decomposition can be avoided if a very small quantity of carbon or calcium carbid is presentin the charge. Under m principle ofv operation where I use a big N energy density and so carry out the complete series of reactions from a cold charge to a finished roduct in a very short interval of time, t ere is little opportunity for the sodium cyanamid produced to decomnitrogen.

.above- 1200"- carbon in the form of free carbon such as lamp black, or preferably of calcium 'carbid. This carbon or carbid addition merely takes care of possible decomposition over the short interval of time during which the charge passes'from temperatures just above redness to temperatures above 1200? G. which time interval can be made as'short as is deemed advisable by properly proportioning the size of the furnace to the amount of energy put into it. V i

In carrying out my process, I, therefore,- find it preferable to use such a form of electric furnace and to. so chose the volume of the active zone and the electric energy applied thereto as will make the time of passage from a cold charge to a fused product self-evident that the process can be made continuous by continuously feeding into the top of the furnace a suitable mixture of cold charge material and tapping out the bottom either continuously or at predetermined in- C., as short as possible. It istervals the melted charge. Also by a suitable predetermined amperage and'voltage I can make the temperature gradient from a cold charge to a finished bath'as steep as is deemed advisable. In commercially carrying out this process, I have found it advis-' able to advance the charge at such a speed that it requires only a few minutes after reacting the temperature of redness to reach a temperature above 1200 C. In the process heretofore proposed it has been customary to either place the charge in the furnace already mixed or else to fuse the chlorid in the furnace first and then to add the cyanamid or lime nitrogen and it took all the way from say four to eight hours to complete the reaction. Further, the furnace had to be'first charged and the reactions completed before any additional charges were placed therein.

My process .over this older batch process, due to the rapid heating-which causes the'inert carbon possesses many advantages to become chemically-active; and also due to my continuously operating furnace as .op-

posed to the slower heating in thelarge batch furnaces, and I obtain a greater efliciency of transformation of cyanamid nitrogen into cyanid nitrogen. This continuous operating furnace is practically self-operatpossesses practically constant ing, in that it electrical conditions in its hearth and is provided with mechanical feed and mechanical tapping, and therefore, needs little or no manual attention. 'On the other hand, the vbatch furnace starting with a cold charge and ending up with a molten charge continuously changes its electrical characteristics with consequent demand for personal attention.

It is evident that a very important feature I of this invention resides in the fact that I cause the graphitic carbon of the lime nitrogen, or the other carbonpresent in the charge, tobe so suddenly raised in temperature as to render it chemically active at once and to thus cause it to unite with the spdium cyanamid substantially as fast as the latter is formed and therefore prevent the objectionable foaming which has been heretofore experienced, .due to the presence of said sodium cyanamid.

Stated in other language, any sodium cyanamid present that is not acted upon by the said graphitic carbon is immediately acted upon by the nascent carbon liberated from the calcium carbid from the charge or it is acted upon by the chemically active carbon which has been addedto the charge'with the result that no foaming at all takes place, and therefore, there is-no tendency, as has V been the case in the older processesyfor the carbon chemically active before any. subevolved gases to raise the charge material or lift it from the vicinity of the molten pool 21. 1

It results that said charge material smoothly and evenl molten pool- 21; an as the temperature is quite high, in said pool 21 the material is so fluid as to readily flow along the tap hole and out of the furnace.

It is obviousl -that those skilled'in the art may vary the details of the process without departing from the spiritof the invention, and therefore, I do not wish tojbe limited -to the above disclosurefexcept as may be refore any substantial foaming takes place,

substantially as described.

3. The process of making an alkali metal cyanid which-consists in providing a mixture of an alkali. metal chlorid, and lime nitrogen containing chemically inactive car: bon;,and raising a portion of said mixture to a temperature sufficient to render said stantial foaming takes place, substantially as described.

4. The continuous process of making an alkali metal cyanid which consists in proriding, and continuously feeding a mixture works down into the 5. The continuous process of making so dium cyanid which consists in continuously feeding into a furnace a mixture of sodium i" (chlorid, calcium cyanamid and calcium carbid; raising the temperature of successive portions of the mixture above 1100 C. be-

fore any substantial portion of the sodiumv cyanamid suffers decomposition; and drawmg off the product thus produced as it is' formed, substantially as described.

m 6. The process of making an alkali metal cyanid which consists in providing a mixture of an alkali metal chlorid, and lime,

nitrogen containing chemically inactive carbon continuouslyfeedin'g said 'mixturei'i'it'o a furnace; continuously raising portions of said mlxture to a temperature sufliclent to render the said carbon chemically active 7 before any'substantial foaming takes place;

and drawing ofl successive portions of the product-thus produced as fast as they are formed, substantially as described.

7. The process of making sodium cyanid which consists in providing a mixture of calcium cyanamid; sodium chlorid and a substance capable of supplying carbon in the reaction; maintaining a current density through a portion of said mixture sufficient to form the desired cyanid without'producing any substantial amount of foaming; and

drawing off the molten product as formed,

substantially as described. H

8. The process of making sodium cyanid which consists in providing a mixture con taining substantially equal weights of lime nitrogen and sodium chlorid;.and maintaining a current density through a restricted portion of said mixture sufficient to produce the desired cyanid without any substantial foaming while continuing to feed said mixtureto and'to withdraw's aid cyanid from the furnace, substantially as described.

9. The process of making sodium cyanid which. consists in providing a mixture containing carbon and substantially equal weightsof lime nitrogen and sodium chlorid; and maintaining a current density through a restricted portion of said mixture sufficient to produce the desired cyanid without any substantial foaming while continuing to feed saidmixture to and to withdraw said cyanid from the furnace, substantially as described.

10. The process of making sodium cyanid which consists in providing a mixture containing combined carbon in the form of calcium carbid and substantially equal weights of lime nitrogen and sodium chlorid; .and maintaining a current density through a. restricted portion of said mixture sufficient to produce the desired cyanid Without any sub- 5 stantial foaming While continuing to feed said mixture to and to Withdraw said cyanid from the furnace, substantially as described.

HORACE FREEMAN.

Witnesses:

V. G. CHAPMAN, D. I. \NILDE'M. 

